while (scanf("%s", buff) != EOF)如何终止？
答：ctrl z+换行 是规定，ctrl c 是发送信号杀死进程（一般不建议ctrl c）。
int main()
{
string str;
while (cin >> str) // operator>>(cin, str)
{
cout << str << endl;
}
char buff[128];
while (scanf("%s", buff) != EOF)
{
printf("%s\n", buff);
}
return 0;
}
1.operator bool
operator bool：本质是为了支持Date对象转换成bool
istream类型对象转换为逻辑条件判断值
实际上我们看到使用while(cin>>i)去流中提取对象数据时，调用的是operator>>，返回值是
istream类型的对象，那么这里可以做逻辑条件值，源自于istream的对象又调用了operator
bool，operator bool调用时如果接收流失败，或者有结束标志，则返回false。
#include<iostream>
#include<string>
#include<fstream>
#include<sstream>
using namespace std;
class Date
{
friend ostream& operator << (ostream& out, const Date& d);
friend istream& operator >> (istream& in, Date& d);
public:
Date(int year = 1, int month = 1, int day = 1)
:_year(year)
, _month(month)
, _day(day)
{}
// 支持Date对象转换成bool
operator bool()
{
// 这里是随意写的，假设输入_year为0，则结束
if (_year < 1)
return false;
else
return true;
}
private:
int _year;
int _month;
int _day;
};
int main()
{
Date d1 = -1;
Date d2 = { 2022, 10, 11 };
bool ret1 = d1;
bool ret2 = d2;
cout << ret1 << endl;
cout << ret2 << endl;
if (d1) 这里本质上也是调用了operator bool
{
}
return 0;
}2.文件读取 ifstream
（1）get()每次读一个字符
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
ifstream ifs("Test.cpp");
while (ifs)
{
char ch = ifs.get();
cout << ch;
}
return 0;
}
（2）>> 自动过滤空格和换行
>>认为空格/换行只是一个间隔，会自动忽略
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
ifstream ifs("Test.cpp");
char ch;
while (ifs>>ch)
{
cout << ch;
}
return 0;
}
（3）拷贝文件
（4）二进制读写
#include<iostream>
#include<fstream>
using namespace std;
struct ServerInfo
{
char _address[256];
这里只能用数组，不能string，string是指针，进程A写入，进程B读取string时就是野指针
//string _address;
int _port;
};
struct ConfigManager
{
public:
ConfigManager(const char* filename)
:_filename(filename)
{}
void WriteBin(const ServerInfo& info)
{
// 1 2 4 8 16
ofstream ofs(_filename, ios_base::out | ios_base::binary);
ofs.write((const char*)&info, sizeof(info));
}
void ReadBin(ServerInfo& info)
{
ifstream ifs(_filename, ios_base::in | ios_base::binary);
ifs.read((char*)&info, sizeof(info));
}
private:
string _filename; // 配置文件
};
int main()
{
ServerInfo winfo = { "https://legacy.cplusplus.com/reference/ios/ios/eof/", 80 };
二进制写：
ConfigManager cf_bin("test.bin"); //打开文件test.bin即可看到
cf_bin.WriteBin(winfo);
二进制读：
ServerInfo rbinfo;
cf_bin.ReadBin(rbinfo);
cout << rbinfo._address << " " << rbinfo._port << " ";
return 0;
}
（5）
struct ServerInfo
{
string _address;
int _port;
Date _d;
};
struct ConfigManager
{
public:
ConfigManager(const char* filename)
:_filename(filename)
{}
// 文本读写
void WriteText(const ServerInfo& info)
{
// 1 2 4 8 16
ofstream ofs(_filename);
ofs << info._address << endl;
ofs << info._port << endl;
ofs << info._d << endl;
}
void ReadText(ServerInfo& info)
{
ifstream ifs(_filename);
ifs >> info._address;
ifs >> info._port;
ifs >> info._d;
}
private:
string _filename; // 配置文件
};
int main()
{
ServerInfo winfo = { "https://legacy.cplusplus.com/reference/ios/ios/eof/"
, 80, {2022, 10, 11} };
ConfigManager cf_txt("test.txt");
cf_txt.WriteText(winfo);
ConfigManager cf_text("test.txt");
ServerInfo rtinfo;
cf_text.ReadText(rtinfo);
cout << rtinfo._address << " " << rtinfo._port << " " << rtinfo._d << endl;
return 0;
}
